Liquid refrigerant pumping system

ABSTRACT

A lubricant supply system includes first and second tanks, each including an internal volume that is divided into a first portion and a second portion. The first portion of the internal volume of the first tank and the first portion of the internal volume of the second tank are configured to alternate supplying a liquid refrigerant to a machine. A pump is in fluid communication with the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank. The pump is configured to vary a pressure of a gas in the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 14/561,692, filed on Dec. 5, 2014, the entirety of which is incorporated herein by reference.

BACKGROUND

A centrifugal compressor includes one or more impellers that compress a fluid. The impellers are mounted on a rotating shaft which is supported by a plurality of bearings. The bearings require a steady supply of lubricant, which is oftentimes oil. However, in some recent applications, refrigerant has been used to lubricate the bearings rather than oil. Refrigerant lubrication can be used when, for example, the compressor is part of a refrigeration chiller. A refrigeration chiller removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. The cooled liquid may then be used to cool air (e.g., air conditioning) or in an industrial process.

A pump can be used to make the refrigerant to flow to the bearings. The pump may cavitate making it more difficult to supply the refrigerant to the bearings. There can also be operating conditions under which the supply of refrigerant is in inadequate supply or the state of the refrigerant is a mix of liquid and vapor such that it is unable to properly lubricate the bearings. Therefore, what is needed is a backup lubricant supply system that is capable of providing lubricant (e.g., refrigerant) to the bearings when the primary lubricant supply system is unable to lubricate the bearings.

SUMMARY

A lubricant supply system is disclosed. The lubricant supply system includes first and second tanks, each including an internal volume that is divided into a first portion and a second portion. The first portion of the internal volume of the first tank and the first portion of the internal volume of the second tank are configured to alternate supplying a liquid refrigerant to a machine. A pump is in fluid communication with the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank. The pump is configured to vary a pressure of a gas in the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.

In another embodiment, the lubricant supply system includes first and second tanks, each including an internal volume that is divided into a first portion and a second portion. The system also includes a refrigeration chiller including an evaporator and a condenser. A valve is in fluid communication with the first portion of the internal volume of the first tank, the evaporator, and the condenser. The valve provides a path of fluid communication from the evaporator to the first portion of the internal volume of the first tank when the valve is in a first position, and the valve provides a path of fluid communication from the condenser to the first portion of the internal volume of the first tank when the valve is in a second position. A pump is in fluid communication with the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank. The pump is configured to vary a pressure of a gas in the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.

A method for supplying a liquid refrigerant to a machine is also disclosed. The method includes causing a pressure of a gas in a first tank to decrease, which draws a liquid refrigerant into the first tank from a refrigeration chiller. A pressure of a gas in second first tank may be caused to decrease, which draws additional liquid refrigerant into the second tank from the refrigeration chiller. The pressure of the gas in the first tank may be caused to increase simultaneously with the pressure of the gas in the second tank decreasing, which causes the liquid refrigerant to flow from the first tank to a bearing in a compressor in the refrigeration chiller.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitutes a part of this specification, illustrates an embodiment of the present teachings and together with the description, serves to explain the principles of the present teachings. In the figures:

FIG. 1 illustrates a schematic view of a system for supplying a lubricant to a machine, according to an embodiment.

FIG. 2 illustrates a schematic view of the system showing the divider as a piston, according to an embodiment.

FIG. 3 illustrates a schematic view of the system showing the divider as a bladder, according to an embodiment.

FIG. 4 illustrates a flowchart of a method for providing lubrication to a machine, according to an embodiment.

FIG. 5 illustrates a schematic view of another system for supplying lubricant to a machine, according to an embodiment.

FIG. 6 illustrates another flowchart of a method for providing lubrication to a machine, according to an embodiment.

It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawing. In the drawings, like reference numerals have been used throughout to designate identical elements, where convenient. In the following description, reference is made to the accompanying drawings that form a part of the description, and in which is shown by way of illustration one or more specific example embodiments in which the present teachings may be practiced.

Further, notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein.

Additionally, when referring to a position or direction in a well, the terms “above,” “up,” “upward,” “ascend,” and various grammatical equivalents thereof may be used to refer to a position in a well that is closer to the surface than another position, or a movement or direction proceeding toward the surface (topside), without regard as to whether the well is vertical, deviated, or horizontal. Similarly, when referring to a position in a well, the terms “below,” “down,” “downward,” and “descend” and various grammatical equivalents thereof may be used to refer to a position in a well that is farther from the surface than another position, or a direction or movement proceeding away from the surface, regardless of whether the well is vertical, deviated, or horizontal. Moreover, the terms “upper,” “lower,” “above,” and “below,” when referring to components of an apparatus, are used to conveniently refer to the relative positioning of components or elements, e.g., as illustrated in the drawings, and may not refer to any particular frame of reference. Thus, a component may be flipped or viewed in any direction, while parts thereof may remain unchanged in terms of being “upper” or “lower” etc.

FIG. 1 illustrates a schematic view of a system 100 for supplying a lubricant to a machine 160, according to an embodiment. The system 100 may include a tank 110 that defines an internal volume. A divider 112 may be positioned in the internal volume of the tank 110 that divides or separates the internal volume into two or more portions (two are shown: 114, 116). As shown, the divider 112 may be a diaphragm that is coupled to the inner surface of the tank 110. The diaphragm 112 may be made of a material that is configured to bend or flex as the first portion of the internal volume 114 increases and decreases in response to a pressure differential between the first and second portions of the internal volume 114, 116.

The tank 110 may have one or more openings (four are shown: 122, 132, 142, 152) that provide a path of fluid communication between the internal volume and the exterior of the tank 110. A first pump 120 (referred to hereafter as a liquid pump) may be in fluid communication with the first portion of the internal volume 114 of the tank 110 through a first one of the openings 122. As used herein, the term “pump” refers to all machines operable to increase and/or decrease a pressure in any type of fluid, whether gas, liquid, or a combination thereof. The liquid pump 120 may be used to introduce a liquid lubricant into the first portion of the internal volume 114 of the tank 110. The lubricant may be an oil or a refrigerant. Illustrative refrigerants may include R-134a, R-123, R-1233zd, R-1234ze, and the like. To prevent lubricant from flowing back through the liquid pump 120, a check valve may be positioned at the discharge end of the liquid pump 120. Alternatively, with the liquid pump 120 running, lubricant cannot flow back through the liquid pump 120.

A valve 130 may be in fluid communication with the second portion of the internal volume 116 of the tank 110 through a second one of the openings 132. The valve 130 may be used to allow gas to discharge (i.e. “bleed off”) from the second portion of the internal volume 116 of the tank 110 when the lubricant is being introduced into the first portion of the internal volume 114.

A second pump 140 (referred to hereafter as a vacuum pump) may be in fluid communication with the second portion of the internal volume 116 of the tank 110 through a third one of the openings 142. The vacuum pump 140 may be used to withdraw the gas from the second portion of the internal volume 116 to reduce the pressure of the gas and leave behind a partial vacuum.

A third pump 150 (referred to hereafter as a gas pump) may be in fluid communication with the second portion of the internal volume 116 of the tank 110 through a fourth one of the openings 152. The gas pump 150 may be used to introduce a gas into the second portion of the internal volume 116 of the tank 110. As such, the gas pump 150 may be or include a compressor. The gas may be air.

Referring again to the first opening 122 in the tank 110, the first opening 122 may also be in fluid communication with a machine 160 via a conduit 162. In at least one embodiment, a valve 124 may be positioned in the conduit 162 between the tank 110 and the machine 160. A sensor (not shown) may be configured to sense when the lubricant supply to the machine 160 (e.g., from a primary lubricant supply system) is insufficient. When this occurs, the valve 124 may be switched from a closed position to an open position (e.g., manually or automatically) to supply the lubricant from the tank 110 to the machine 160.

The machine 160 may be any machine having relative movement between two or more components. As shown, the machine 160 is a centrifugal compressor in a chiller (e.g., a refrigeration chiller). The “chiller” removes heat from a liquid (e.g., liquid refrigerant lubricant) via a vapor-compression cycle or an absorption refrigeration cycle. For example, the liquid refrigerant lubricant may flow through an evaporator of the chiller where heat is transferred to a first heat transfer fluid. The first heat transfer fluid may flow through machine (e.g., compressor) 160 where the pressure may be increased. The first heat transfer fluid (now compressed) may then be introduced to a condenser of the chiller where the heat is transferred from the first heat transfer fluid to a second heat transfer fluid. The liquid refrigerant lubricant may be discharged from the evaporator and be circulated through a heat exchanger to cool air or equipment as desired. In another embodiment, the liquid refrigerant lubricant may be discharged from the condenser of the chiller depending on the operating conditions of the compressor chiller 160 and the state of the refrigerant.

As shown, the machine (e.g., compressor) 160 may include at least one impeller 170. The machine (e.g., compressor) 160 may include a shaft 172 that is configured to rotate about a central longitudinal axis 174. The shaft 172 may be supported by one or more bearings (four are shown: 176). The bearings 176 may each include an inner ring or “race” 178, an outer ring or race 180, and one or more rolling elements (e.g., balls) 182 positioned therebetween. As described in greater detail below, the liquid refrigerant lubricant may flow from the first portion of the internal volume 114 of the tank 110 and be introduced to the bearings 176 (e.g., between the inner and outer rings 178, 180). In some embodiments, the bearings 176 may have steel or ceramic rolling elements.

FIG. 2 illustrates a schematic view of the system 100 showing the divider 112 as a piston, according to an embodiment. In at least one embodiment, rather than the divider 112 being a diaphragm (as shown in FIG. 1), the divider 112 may be a piston (as shown in FIG. 2). The piston 212 may be positioned within the tank 110 and divide or separate the internal volume into the two portions 114, 116. The piston 212 may be configured to move within the tank 110 as the first portion of the internal volume 114 increases and decreases in response to a pressure differential between the first and second portions of the internal volume 114, 116. For example, the piston 212 may move in a first axial direction 214 (e.g., down as shown in FIG. 2) when the pressure of the gas in the second portion of the internal volume 116 is greater than the pressure of the lubricant in the first portion of the internal volume 114. Similarly, the piston 212 may move in a second axial direction 216 (e.g., up as shown in FIG. 2) when the pressure of the lubricant in the first portion of the internal volume 114 is greater than the pressure of the gas in the second portion of the internal volume 116.

FIG. 3 illustrates a schematic view of the system 100 showing the divider 112 as a bladder, according to an embodiment. In at least one embodiment, rather than the divider 112 being a diaphragm (as shown in FIG. 1) or a piston (as shown in FIG. 2), the divider 112 may be a bladder (as shown in FIG. 3). The bladder 312 may be positioned within the tank 110 and divide or separate the internal volume into the two portions 114, 116. More particularly, the bladder 312 may include a flexible “bag” that defines an internal volume that is configured to receive the lubricant. In at least one embodiment, the bladder 312 may be made from a polymer or elastomer (e.g., rubber). The bladder 312 may include an opening that is in fluid communication with the first opening 122 in the tank 110.

With continuing reference to FIGS. 1-3, FIG. 4 illustrates a flowchart of a method 400 for providing lubrication to a machine, according to an embodiment. The method 400 may proceed by operation of an embodiment of the system 100, for example, and may thus be best understood with reference thereto. However, it will be appreciated that the method 400 is not limited to any particular structure unless otherwise stated herein. In addition, the steps below may be conducted in any order, and the order described below is for illustrative purposes only.

The method 400 may include introducing a lubricant (e.g., a refrigerant) into a first portion of an internal volume of a tank, as at 402. In one embodiment, the lubricant may be pumped into the first portion of the internal volume with a first or “liquid” pump. A valve that is in fluid communication with a second portion of the internal volume of the tank may be open as the lubricant is pumped into the first portion of the internal volume of the tank. This may allow a gas within the second portion of the internal volume to discharge from the second portion of the internal volume to make room for the lubricant in the first portion of the internal volume. The valve may be closed once the lubricant is stored in the first portion of the internal volume.

In another embodiment, instead of, or in addition to, using the liquid pump to introduce the lubricant into the first portion of the internal volume, a second or “vacuum” pump may withdraw at least a portion of the gas from the second portion of the internal volume, leaving behind a partial vacuum in the second portion of the internal volume. This partial vacuum may draw the lubricant into the first portion of the internal volume.

The method 400 may also include increasing a pressure of the gas in the second portion of the internal volume of the tank, as at 404. In one embodiment, additional gas (e.g., air) may be pumped into the second portion of the internal volume with a third or “gas” pump to increase the pressure in the second portion of the internal volume. The gas pump may be controlled to maintain a predetermined pressure in the first portion of the internal volume and/or the second portion of the internal volume. For example, the pressurized gas in the second portion of the internal volume may exert a force on the lubricant in the first portion of the internal volume via a diaphragm, a piston, a bladder, or the like positioned between the first and second portions. This may cause the pressure of the lubricant in the first portion of the internal volume to increase, and the pressure may be maintained at this level until the lubricant is released to a machine, as discussed below. In one embodiment, the vacuum and gas pumps may be a single pump that includes a switch at the inlet and outlet sides so that it may serve to increase and decrease the pressure of the gas based on the position of the switch.

The method 400 may also include supplying the lubricant from the tank to a machine, as at 406. More particularly, a sensor may sense when the lubricant supplied to the machine (e.g., from a primary lubrication system) is insufficient. When this occurs, a valve positioned between the tank and the machine may be switched to an open position, and the (now pressurized) lubricant may flow through the valve and to the machine. The lubricant may be supplied to one or more bearings in the machine. By using back pressure to facilitate the flow of the lubricant, the lubricant may flow easier than when compared to a conventional gravity-fed system. In addition, by using back pressure, the lubricant may be supplied in a sub-cooled liquid state.

FIG. 5 illustrates a schematic view of another system 500 for supplying lubricant to the machine 160, according to an embodiment. The system 500 may include one or more accumulator tanks (two are shown 510, 550 that each define an internal volume. The first tank 510 may have a divider 512 positioned in the internal volume that divides or separates the internal volume into two or more portions (two are shown: 514, 516). Similarly, the second tank 550 may have a divider 552 positioned in the internal volume that divides or separates the internal volume into two or more portions (two are shown: 554, 556). The dividers 512, 552 may be diaphragms, pistons, bladders, or the like.

The first portion of the internal volume 514 of the first tank 510 may be in fluid communication with a refrigeration chiller 502 and configured to receive lubricant therefrom. The lubricant may be oil or a liquid refrigerant. In at least one embodiment, a valve 520 may be positioned between the refrigeration chiller 502 and the first tank 510. As shown, the valve 520 may be a three way valve that is in fluid communication with the first portion of the internal volume 514 of the first tank 510, an evaporator 504 of the refrigeration chiller 502, and a condenser 506 of the refrigeration chiller 502. When the valve 520 is in a first position, a path of fluid communication may exist from the evaporator 504, through the valve 520, and to the first portion of the internal volume 514 of the first tank 510. When the valve 520 is in a second position, a path of fluid communication may exist from the condenser 506, through the valve 520, and to the first portion of the internal volume 514 of the first tank 510. A check valve 522 may also be positioned between the refrigeration chiller 502 and the first tank 510. The check valve 522 may allow the lubricant to flow from the refrigeration chiller 502 to the first tank 510, but not from the first tank 510 to the refrigeration chiller 502.

The first portion of the internal volume 514 of the first tank 510 may also be in fluid communication with the machine (e.g., compressor) 160 in the refrigeration chiller 502. More particularly, the lubricant may be supplied from the first portion of the internal volume 514 of the first tank 510 to the bearings 176 of the machine 160. A check valve 524 may be positioned between the first tank 510 and the machine 160. The check valve 524 may allow the lubricant to flow from the first portion of the internal volume 514 of the first tank 510 to the machine 160, but not from the machine 160 to the first portion of the internal volume 514 of the first tank 510. In at least one embodiment, a shut-off valve 526 may also be positioned between the first portion of the internal volume 514 of the first tank 510 and the refrigeration chiller 502, between the first portion of the internal volume 514 of the first tank 510 and the machine 160, or both.

The first portion of the internal volume 554 of the second tank 550 may also be in fluid communication with the refrigeration chiller 502 and configured to receive lubricant therefrom. In at least one embodiment, a valve 560 may be positioned between the refrigeration chiller 502 and the second tank 550. As shown, the valve 560 may be a three way valve that is in fluid communication with the first portion of the internal volume 554 of the first tank 550, the evaporator 504 of the refrigeration chiller 502, and the condenser 506 of the refrigeration chiller 502. When the valve 560 is in a first position, a path of fluid communication may exist from the evaporator 504, through the valve 560, and to the first portion of the internal volume 554 of the second tank 550. When the valve 560 is in a second position, a path of fluid communication may exist from the condenser 506, through the valve 560, and to the first portion of the internal volume 554 of the second tank 550. A check valve 562 may also be positioned between the refrigeration chiller 502 and the second tank 550. The check valve 562 may allow the lubricant to flow from the refrigeration chiller 502 to second first tank 550, but not from the second tank 550 to the refrigeration chiller 502.

The first portion of the internal volume 554 of the second tank 550 may also be in fluid communication with the machine (e.g., compressor) 160. More particularly, the lubricant may be supplied from the first portion of the internal volume 554 of the second tank 550 to the bearings 176 of the machine 160. A check valve 564 may be positioned between the second tank 550 and the machine 160. The check valve 564 may allow the lubricant to flow from the first portion of the internal volume 554 of the second tank 550 to the machine 160, but not from the machine 160 to the first portion of the internal volume 554 of the second tank 550. In at least one embodiment, a shut-off valve 566 may also be positioned between the first portion of the internal volume 554 of the second tank 550 and the refrigeration chiller 502, between the first portion of the internal volume 554 of the second tank 550 and the machine 160, or both.

A pump 570 may be in fluid communication with the second portion of the internal volume 516 of the first tank 510 and the second portion of the internal volume 556 of the second tank 550. The pump 570 may be used to vary a pressure of a gas into the second portion of the internal volume 516 of the first tank 510 and the second portion of the internal volume 556 of the second tank 550. More particularly, the pump 570 may be used to transfer a gas back and forth between the second portion of the internal volume 516 of the first tank 510 and the second portion of the internal volume 556 of the second tank 550. As such, the pump 570 may be or include a compressor. The gas may be nitrogen or air. When the pump 570 is operating in a substantially closed circuit between the first and second tanks 510, 550, as described above, gas may be added to the circuit to offset any leakage.

To prevent lubricant from flowing back through the pump 570, a check valve may be positioned at the discharge end of the pump 570. Alternatively, with the pump 570 running, lubricant cannot flow back through the pump 570. In at least one embodiment, the pump 570 may be or include first and second pumps where the first pump is in fluid communication with the second portion of the internal volume 516 of the first tank 510, and the second pump is in fluid communication with the second portion of the internal volume 556 of the second tank 550.

With continuing reference to FIG. 5, FIG. 6 illustrates a flowchart of a method 600 for providing lubrication to a machine, according to an embodiment. The method 600 may proceed by operation of an embodiment of the system 500, for example, and may thus be best understood with reference thereto. However, it will be appreciated that the method 600 is not limited to any particular structure unless otherwise stated herein. In addition, the steps below may be conducted in any order, and the order described below is for illustrative purposes only.

The method 600 may include pumping gas (e.g., nitrogen) from the second portion of the internal volume 516 of the first tank 510 to the second portion of the internal volume 556 of the second tank 550 using the pump 570, as at 602. This may cause the pressure in the first tank 510 to decrease. The shut-off valve 526 proximate to the first tank 510 may be opened, allowing lubricant to be drawn into the first portion of the internal volume 514 of the first tank 510 from the evaporator 504 of the refrigeration chiller 502, as at 604. Once a predetermined amount of the lubricant is within the first portion of the internal volume 514 of the first tank 510 (e.g., filling about 50% of the first tank 510), the shut-off valve 526 proximate to the first tank 510 may be closed, as at 606.

The pump 570 may then reverse direction by pumping at least a portion of the gas from the second portion of the internal volume 556 of the second tank 550 into the second portion of the internal volume 516 of the first tank 510, as at 608. This may cause the pressure in the second tank 550 to decrease. The shut-off valve 566 proximate to the second tank 550 may be opened, allowing additional lubricant to be drawn into the first portion of the internal volume 554 of the second tank 550, as at 610. Once a predetermined amount of the lubricant is within the first portion of the internal volume 554 of the second tank 550 (e.g., filling about 50% of the second tank 550), the shut-off valve 566 proximate to the second tank 550 may be closed, as at 612.

The system 500 is now ready to lubricate the bearings 176 of the machine (e.g., compressor) 160. The shut-off valve 526 proximate to the first tank 510 may be opened, as at 614. The pressurized gas in the second portion of the internal volume 516 of the first tank 510 may exert a force on the divider 512, causing the lubricant to flow from the first portion of the internal volume 514 of the first tank 510 to the bearings 176 of the machine 160. The pump 570 may cause an additional portion of the gas to flow from the second portion of the internal volume 556 of the second tank 550 to the second portion of the internal volume 516 of the first tank 510, as at 616. This may maintain or increase the pressure in the first tank 510 so that the lubricant may continue to flow to the bearings 176.

When the lubricant in the first portion of the internal volume 514 of the first tank 510 drops below a predetermined amount (e.g., less than 10% of the first tank 510 contains lubricant), the pump 570 may reverse direction and transfer at least a portion of the gas from the second portion of the internal volume 516 of the first tank 510 to the second portion of the internal volume 556 of the second tank 550, as at 618. The shut-off valve 526 proximate to the first tank 510 may be closed, and the shut-off valve 566 proximate to the second tank 550 may be opened, as at 620. The pressurized gas in the second portion of the internal volume 556 of the second tank 550 may cause the lubricant to flow from the first portion of the internal volume 554 of the second tank 550 to the bearings 176 of the machine 160.

The method 600 may loop back to block 604 where the shut-off valve 526 proximate to the first tank 510 may be opened again, allowing additional lubricant to be drawn into the first portion of the internal volume 514 of the first tank 510 from the evaporator 504 (e.g., simultaneously with lubricant flowing from the second tank 550 to the bearings 176 of the machine 160). Thus, the tanks 510, 550 may alternate receiving the lubricant from the evaporator 504, and the bearings 176 of the machine 160 may alternate receiving the lubricant from the tanks 510, 550.

The first and second tanks 510, 550 may initially (e.g., during start-up) draw in the lubricant from the evaporator 504 of the refrigeration chiller 502. Once the refrigeration chiller 502 reaches steady state conditions, the valves 520, 560 may be switched to the second position such that the first and second tanks 510, 550 may draw in the lubricant from the condenser 506 of the refrigeration chiller 502.

While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal.

Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the specification and practice of the present teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims. 

What is claimed is:
 1. A lubricant supply system, comprising: a first tank defining an internal volume that is divided into a first portion and a second portion; a second tank defining an internal volume that is divided into a first portion and a second portion, wherein the first portion of the internal volume of the first tank and the first portion of the internal volume of the second tank are configured to alternate supplying a liquid refrigerant to a machine; and a pump in fluid communication with the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank, wherein the pump is configured to vary a pressure of a gas in the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.
 2. The lubricant supply system of claim 1, wherein the first portion of the internal volume of the first tank and the first portion of the internal volume of the second tank are configured to be in fluid communication with a refrigeration chiller and to receive the liquid refrigerant therefrom.
 3. The lubricant supply system of claim 2, wherein the pump is configured to transfer at least a portion of the gas from the second portion of the internal volume of the first tank to the second portion of the internal volume of the second tank, thereby generating a pressure differential that draws the liquid refrigerant from the refrigeration chiller into the first portion of the internal volume of the first tank.
 4. The lubricant supply system of claim 2, wherein the pump is configured to transfer at least a portion of the gas back and forth between the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.
 5. The lubricant supply system of claim 4, wherein the first portion of the internal volume of the first tank and the first portion of the internal volume of the first tank are configured to alternate drawing the liquid refrigerant from the refrigeration chiller based on operation of the pump.
 6. The lubricant supply system of claim 1, wherein the pump comprises: a first pump in fluid communication with the second portion of the internal volume of the first tank; and a second pump in fluid communication with the second portion of the internal volume of the second tank.
 7. The lubricant supply system of claim 1, wherein the first and second portions of the internal volume of the first tank are separated by a divider, and wherein the divider comprises a diaphragm, a piston, or a bladder.
 8. A lubricant supply system, comprising: a first tank defining an internal volume that is divided into a first portion and a second portion; a second tank defining an internal volume that is divided into a first portion and a second portion; a refrigeration chiller including an evaporator and a condenser; a valve in fluid communication with the first portion of the internal volume of the first tank, the evaporator, and the condenser, wherein the valve provides a path of fluid communication from the evaporator to the first portion of the internal volume of the first tank when the valve is in a first position, and wherein the valve provides a path of fluid communication from the condenser to the first portion of the internal volume of the first tank when the valve is in a second position; and a pump in fluid communication with the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank, wherein the pump is configured to vary a pressure of a gas in the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.
 9. The lubricant supply system of claim 8, wherein the pump is configured to simultaneously increase the pressure of the gas in the second portion of the internal volume of the first tank and decrease the pressure of the gas in the second portion of the internal volume of the second tank.
 10. The lubricant supply system of claim 9, wherein the increased pressure in the second portion of the internal volume of the first tank causes a liquid refrigerant to flow from the first portion of the internal volume of the first tank to one or more bearings in a compressor in the refrigeration chiller.
 11. The lubricant supply system of claim 10, wherein the decreased pressure in the second portion of the internal volume of the second tank causes additional liquid refrigerant to be drawn into the first portion of the internal volume of the second tank from the evaporator or the condenser.
 12. The lubricant supply system of claim 11, wherein the pump is configured to transfer at least a portion of the gas back and forth between the second portion of the internal volume of the first tank and the second portion of the internal volume of the second tank.
 13. The lubricant supply system of claim 11, wherein the pump comprises: a first pump in fluid communication with the second portion of the internal volume of the first tank; and a second pump in fluid communication with the second portion of the internal volume of the second tank.
 14. A method for supplying a liquid refrigerant to a machine, comprising: causing a pressure of a gas in a first tank to decrease, which draws a liquid refrigerant into the first tank from a refrigeration chiller; causing a pressure of a gas in second first tank to decrease, which draws additional liquid refrigerant into the second tank from the refrigeration chiller; and causing the pressure of the gas in the first tank to increase simultaneously with the pressure of the gas in the second tank decreasing, which causes the liquid refrigerant to flow from the first tank to a bearing in a compressor in the refrigeration chiller.
 15. The method of claim 14, further comprising causing the pressure of the gas in the second tank to increase simultaneously with the pressure of the gas in the first tank decreasing, which causes the additional liquid refrigerant to flow from the second tank to the bearing in the compressor.
 16. The method of claim 14, wherein a pump causes the pressure of the gas in the first tank to increase simultaneously with the pressure of the gas in the second tank decreasing by transferring at least a portion of the gas in the first tank to the second tank.
 17. The method of claim 14, further comprising actuating a valve from a first position to a second position, wherein the liquid refrigerant flows from an evaporator of the refrigeration chiller, through the valve, and to the first tank when the valve is in the first position, and wherein the liquid refrigerant flows from a condenser of the refrigeration chiller, through the valve, and to the first tank when the valve is in the second position.
 18. The method of claim 14, wherein the first and second tanks alternate supplying the liquid refrigerant and the additional liquid refrigerant to the bearing in the compressor.
 19. The method of claim 14, further comprising closing a shut-off valve positioned proximate to an opening in the first tank through which the liquid refrigerant flows before the pressure of the gas in the first tank decreases.
 20. The method of claim 14, wherein the gas in the first tank and the liquid refrigerant in the first tank are separated by a divider, and wherein the divider comprises a diaphragm, a piston, or a bladder. 